The Influence of Prehospital Times on Trauma Mortality

Emergency medical services (EMS) are a crucial component of high performing systems. The impact of EMS and prehospital trauma system factors on trauma mortality is understudied. This thesis seeks to clarify the role of EMS prehospital times, one important system-level factor, on trauma mortality at the hospital and population-levels. In the first part of the thesis, the influence of prehospital times on trauma center mortality is investigated. Because differences in prehospital times might influence the likelihood that patients with negligible chance of survival (so-called “unsalvageable” patients) will arrive at the emergency department (ED), a case definition for such patients is established. A PROXY definition for the unsalvageable patient based on objective ED metrics (SBP=0, HR=0, GCS=3) is tested. Construct validity and relevance to trauma center benchmarking is demonstrated. Applying the PROXY definition, the influence of prehospital times on trauma center performance is examined. Using novel linkage of the National EMS Information System (NEMSIS) database to trauma centers participating in the Trauma Quality Improvement Program, shorter prehospital times are found to be strongly associated with ED mortality. However, no association between prehospital time and overall trauma center mortality is observed after risk-adjustment. In the second part of the thesis, influence of EMS response times on mortality from motor vehicle crashes (MVCs) is investigated. Using data derived from the Fatality Analysis Reporting System (FARS) of the National Highway Traffic Safety Administration, the role of EMS response times on regional differences in prehospital death from MVCs is examined. After adjusting for potential confounders at the occupant, vehicle, and crash-levels, EMS response times are found to be significantly associated with risk of prehospital death. Finally, using novel linkage of NEMSIS and FARS data, the relationship between EMS response time and MVC mortality is examined at the population-level within 2,268 United States counties. After adjusting for age, gender, on-scene and transport times, access to trauma resources, state traffic safety laws, and rurality, longer EMS response times are found to be strongly associated with greater rates of MVC-related death.Ph.D